What are Endocrine Disruptors?
Nicole Cassey
Founder, HeraVita
"When I started researching what goes into conventional activewear, I kept coming back to one question I couldn't shake: if I already know my hormones are under pressure during perimenopause, why would I wear something that adds to that load? The answer, once I understood what endocrine disruptors actually are, was that I wouldn't. And I'd never make anything that did."
Start here: what the endocrine system actually does
Your endocrine system is the body's chemical messaging network. It's made up of glands, including the thyroid, adrenal glands, ovaries and pancreas, that produce hormones and release them into the bloodstream. Those hormones travel to organs and tissues, where they regulate almost everything: metabolism, sleep, mood, fertility, immune function, and how the body responds to stress.
In midlife, this system is already navigating significant change. Oestrogen and progesterone levels shift, sometimes gradually, sometimes dramatically. The thyroid works harder. The adrenal glands pick up some of the hormonal slack. It's a delicate recalibration, and it's happening continuously, whether you notice it or not.
When that system functions well, you often don't think about it. When something disrupts it, you feel it everywhere.
"Endocrine disruptors are chemicals that interfere with your body's hormonal messaging, mimicking, blocking or altering the signals your glands are trying to send."
So what is an endocrine disruptor?
An endocrine disruptor is any chemical that interferes with the body's hormonal system. They do this in several ways: some mimic hormones, binding to the same receptors your natural hormones use and triggering responses the body didn't intend. Others block hormones from binding at all, effectively silencing signals. Others alter the rate at which your body produces, breaks down or transports hormones.
A substantial body of research now links certain endocrine-disrupting chemicals with hormone-related health effects, although risk varies by chemical, dose, route of exposure and individual vulnerability. The World Health Organisation and the United Nations Environment Programme (UNEP) jointly classify endocrine-disrupting chemicals as a global public health concern ↗ WHO/UNEP 2013, and the Endocrine Society's scientific statement outlines the mechanisms and health associations across reproductive, thyroid and metabolic systems ↗ EDC-2 Statement.
For women already navigating hormonal transition, the question is not whether EDCs cause harm at any dose, it's whether adding a background chemical load is something worth being thoughtful about. We think it is.
The ones commonly found in conventional activewear
Activewear is one of the more chemically intensive categories in fashion. Performance fabrics are treated for moisture-wicking, odour resistance, stretch retention and durability. Many of the chemicals used to achieve those properties have raised questions in the scientific literature around hormonal effects.
PFAS
Per- and polyfluoroalkyl substances
Used for water and stain resistance. Known as "forever chemicals" because they persist in the body and environment. Associated in research with thyroid disruption, immune effects and hormone interference, though the degree of risk varies considerably across the 4,000+ compounds in this class.
Further reading: PFAS dermal absorption study, Environment International 2024 · PFAS-Tox Database
Phthalates
Plasticising agents
Used to make synthetic fabrics more flexible and durable, and present in some dyes and inks. Several phthalates are associated with oestrogenic activity in research. A 2024 review specifically examined phthalate esters in clothing and noted concerns around endocrine disruption and reproductive effects.
Further reading: Phthalate esters in clothing, Science of the Total Environment 2024
BPA & BPS
Bisphenol A and Bisphenol S
Found in some synthetic fabric coatings and dyes, and in recycled textiles. BPA is a well-studied oestrogen mimic. BPS, marketed as a safer alternative, has been shown in research to disrupt hormones through similar mechanisms. Recent textile studies have assessed dermal exposure from both.
Further reading: Bisphenols in clothing and dermal exposure, Chemosphere 2023
Flame retardants
Organophosphates and halogenated compounds
Required by some textile regulations in certain markets. Several commonly used flame retardant classes have documented links to thyroid hormone disruption in the research literature, although regulatory status varies by compound and jurisdiction.
Further reading: Flame retardants and endocrine disruption review, Environmental Health Perspectives
These chemicals are not always disclosed on labels. Fabric composition tells you what a garment is made from, it does not tell you what it has been treated with. A polyester legging labelled "polyester, elastane" may have been processed with chemical finishes that don't appear in the product description.
Why activewear creates a higher-contact environment
Skin can be a route of exposure for some chemicals, particularly where there is heat, friction, sweat, oil and prolonged contact ↗ University of Birmingham research. The extent of dermal absorption varies significantly by chemical type, skin condition and exposure conditions, it is not uniform across all compounds or all people.
What is particular about activewear is the environment it creates: close fit, elevated skin temperature during exercise, sweat, friction, and repeated contact against areas of the body that are both hormonally significant and in some cases more permeable, inner thighs, underarms, abdomen. This doesn't make activewear uniquely dangerous, but it does make it a category worth thinking carefully about when choosing materials.
The strongest argument for natural fibres in activewear is not that all synthetics are toxic. It's that activewear creates conditions, heat, sweat, friction, prolonged close contact, that maximise the opportunity for whatever is in the fabric to interact with your skin. If you can achieve comparable performance with materials that carry less chemical uncertainty, it seems like a reasonable choice to make.
Why this question feels more relevant in midlife
During perimenopause and menopause, oestrogen levels are already fluctuating. Thyroid function, which governs metabolism and energy, can become more sensitive to disruption during this period. The adrenal glands take on some of the hormonal workload as ovarian function changes. None of this means that wearing conventional activewear will cause measurable harm, the research doesn't support that level of certainty. But it does mean that some women in midlife choose to reduce their chemical exposure where they practically can. Clothing is one of those places.
It is not possible to eliminate all environmental chemical exposure. But the clothes you wear every day, especially the ones you exercise in, are a category where the choice is genuinely yours to make.
What to look for when buying activewear
If you want to make more informed choices about the activewear you buy, these are the signals worth looking for:
| ✓ | PFAS-free | Explicitly stated, not implied. Look for brands that confirm no PFAS in fabric treatments or coatings. |
| ✓ | GOTS certified organic cotton | The Global Organic Textile Standard covers the full supply chain from fibre to finished product, including chemical use in processing. |
| ✓ | OEKO-TEX Standard 100 | Tests for a range of harmful substances in finished textiles, including several regulated EDCs. |
| ✓ | Undyed or low-impact dyes | Conventional synthetic dyes can introduce additional chemical compounds; low-impact or undyed fabrics reduce this. |
| ✓ | Full material disclosure | Brands that tell you not just the fibre content but the treatments and finishes applied are worth supporting. |
| ✓ | Caution with performance claims | "Stain-resistant", "water-repellent" and "anti-odour chemical finish" are often signals of chemical treatment. Look for these properties achieved through fibre choice, merino, for example, rather than applied chemistry. |
What HeraVita does differently
HeraVita is built on a simple commitment: we will not use materials we wouldn't trust against our own skin. That means predominantly natural fibres, GOTS certified organic cotton, merino wool, silk, grown and processed without the pesticide and chemical residue loads that conventional textile production carries. And it means no PFAS, no synthetic performance coatings, no endocrine-disrupting finishes applied in pursuit of properties that natural fibres can largely deliver on their own.
Merino wool naturally wicks moisture, regulates temperature and resists odour, without chemistry. Organic cotton breathes and softens over time, without treatment. Silk sits against skin with a gentleness no synthetic can replicate. These are not compromises on performance. They are a different understanding of what performance means, when the person wearing the garment is a woman in midlife whose body is doing enough already.
We also believe that making this choice, and explaining it honestly, including its limits, is part of what it means to build a brand for women who have had enough of products that don't take their health seriously. You deserve to know what's in your activewear. And you deserve activewear built by someone who asked the question in the first place.
